1. Field of the Invention
The present invention generally relates to a magnetic resonance imaging apparatus for obtaining a magnetic resonance information signal of an object (patient) under medical examination. More specifically, the present invention is directed to a magnetic resonance imaging apparatus employing a viewing screen which is observed by the patient during the medical examination.
2. Description of the Related Art
A magnetic resonance imaging apparatus per se is known in the art from, for instance, Japanese Laid-open (KOKAI) Patent Application No. 63-262146 (opened on Oct. 28, 1988). The typical operation of the magnetic resonance imaging apparatus is as follows. A uniform static magnetic field is produced at a desired examining portion of an object under medical examination. A magnetic resonance phenomenon is caused only in a specific slice portion of the object, from which magnetic resonance computerized tomographic images are acquired, by employing a transmitting RF (radio frequency) coil for forming an RF magnetic field perpendicular to this static magnetic field. After the RF magnetic field is deprived from the slice portion, magnetic resonance imaging signals generated from nuclei are received by a receiving RF coil. In addition, gradient magnetic fields are given to the above static field, which have linear gradients with respect to an X'-axis direction (i.e., a coordinate system rotated by an angle from an X axis). As a result, a synthesized magnetic resonance signal is obtained, and thereafter Fourier-transformed in order to obtain various projection information of the slice portion in the predetermined directions within the X-Y plane while rotating the X'-axis in the X-Y plane. As a consequence, a desired computerized tomographic image of the slice portion can be acquired.
In the above-described conventional magnetic resonance imaging apparatus, there is a drawback that since an object under examination is completely inserted into a cylindrical hole having a typical length of 200 cm and a typical diameter of 60 cm of a gantry, he feels anxieties and/or claustrophobia during an examination time. The static magnetic field coil, gradient field coils and other MRI components are mounted on this gantry. A typical examination period is about 1.5 to 2 hours. Specifically, in accordance with the MRI (magnetic resonance imaging) system for acquiring the MRI signals in synchronism with a cardiac beat of a patient, adverse influences in view of medical considerations are given to the acquired MRI signals of the patient who is under such a bad psychological condition.
The present invention has been made in an attempt to solve the above-described problems, and therefore has an object to provide a magnetic resonance imaging apparatus by which a patient is substantially freed himself from the above-described medical conditions and/or psychological problems, e.g., claustrophobia.